Modern vehicles typically have one or more diagnostic systems, generally having separate computer control modules or electronic control units (ECUs) to control various functions of the vehicle. Some examples include a powertrain control module (PCM), engine control module (ECM), transmission control module (TCM), and anti-locking brake system (ABS). The vehicle diagnostic systems often have self-diagnostic capability to detect and alert the driver of problems the vehicle may be encountering. When a problem is found, a diagnostic trouble code (DTC) is set within the computer's memory. DTCs are as general or as specific as the manufacturer desires.
To retrieve and decipher DTCs, an auto repair technician needs to connect to the vehicle and be able to communicate with the vehicle. A device, such as one or a combination of a VCI, a diagnostic tool, a scan tool, a Personal Computer (PC), diagnostic computer or the like is typically used to communicate, retrieve, and decipher the DTCs. In one typical implementation, the VCI translates between the vehicle communication protocol and a PC communication protocol. In this scenario, the PC serves as the user interface portion of the diagnostic system. Alternatively, one could use a scan tool, which would communicate with the vehicle directly and has its own discrete user interface.
The vehicle communication components, such as a VCI, are typically equipped to communicate in various communication protocols such as Controller Area Network (CAN), SAE Jl850 VPW, PWM, ISO 9141, and others. These communication protocols may be specific to the various automobile manufacturers and others may be fairly standardized, at least at the physical layer.
A cable is typically used to interface with the vehicle. Although the vehicle communication components typically have a SAE J 1962 type connector having 16 pins for various communications, power supply, controls and measurements, the use of the different pins for different functions varies between the different modules in the vehicle and can also vary with different manufactures of the vehicles. In some instances, the vehicle communication components may implement other types of connectors and other types of cables may be substituted for the cable with the SAE J 1962 type connector, for example a 38 way connector for Daimler vehicles or a 20 way connector for BMW vehicles or a SAE J1939-13 connector for heavy duty vehicles.
To achieve communication, vehicle communication components such as a VCI may contain multiple protocol drivers and a multiplexing circuit (MUX) capable of connecting a choice of those protocols drivers to a choice of pins of the vehicle diagnostic link connector (DLC). Different protocols operate at different voltage levels and the vehicle manufacturer may use reserved pins of the DLC for different power lines and signals.
A problem known with this methodology involves excessive voltage between one or more of a VCI, a diagnostic tool, a scan tool, a PC, a diagnostic computer, a vehicle, and/or the associated components. For example, as the different protocols operate at different voltage levels, and as the vehicle manufacturer may use reserved pins of the DLC for different power lines and signals, an incorrect connection may lead to a voltage overload situation and potential damage may result in one or more of the VCI, the diagnostic tool, the scan tool, the PC, the diagnostic computer, the vehicle, and/or the associated components.
Accordingly, it is desirable to provide an apparatus and process to protect the vehicle communication components from damage.